1640s, "evergreen," formed in English from Latin perennis "lasting through the year (or years)," from per- "through" (see per) + annus "year" (see annual). Botanical sense of "Remaining alive through a number of years" is attested from 1670s; figurative meaning of "enduring, permanent" is from 1750. Related: Perennially. For vowel change, see biennial. The noun meaning "a perennial plant" is from 1763.